1. Field of Use
This invention relates to filament winding and, more particularly, to filament wound tubes that are connectable with each other. This invention, still more particularly, relates to connecting tubes that are adapted to transmit torsional as well as radial and axial forces and, accordingly, are useful in oil field drilling pipe, drive shafts for transmitting rotary power and suspension components for heavy ground vehicles.
Filament winding is a well known technique for making composite tubes using high strength filaments such as carbon (graphite) fiber and thermosetting resin. Compared to tubes made of metal such as steel, the resultant filament wound tubes are considerably lighter in weight, have equivalent strength and generally have better fatigue resistance. Moreover, the filament wound tubes advantageously do not corrode.
When a composite tube is to be used in a torque transmitting application, however, the tube needs to be connected to another body in a manner enabling torque transmission. A variety of connectors have been proposed in the prior art for this purpose including, for example, the use of rivets, pins and the like which are inserted through holes drilled in the pipe.
Cutting holes in a composite tube is not always advantageous. For example, in oil field drilling pipe, the tube needs to be impermeable to highly pressurized fluids and effective sealing of the holes in the pipe is difficult. Moreover, when significant torsional and bending loads are applied to the tubes having such pins, rivets and the like, these fasteners undergo significant loads and may break or otherwise cause excessive wear around the holes in the composite tube.
The use of an upset region at the end of a filament wound tube has also been disclosed in the prior art. See, also, U.S. Ser. No. 843,425 filed Mar. 24, 1986 now U.S. Pat. No. 4,813,715 in the name of F. J. Policelli which is herein incorporated by reference. The instant tube is different than the tube in said U.S. Ser. No. 843,425 in its use of round outer surfaces on its connecting composite ends.
2. Objects of the Invention
It is an object of this invention to provide a low cost, high performance connecting tube that has a highly reliable means for connection.
It is an object of this invention to provide a connecting composite tube which can transmit very high torsional forces in addition to high axial forces and internal pressure.
It is an object of this invention to provide a connecting tube for use in applications such as oil field drilling pipe, shafts that transmit rotary power and suspension components for heavy ground vehicles wherein the connecting tube has a joint with a diameter that is minimized through connecting members whose strength is optimized.